Deployment of a Novel Proppant Coating Technology for Controlling Airborne Dust in the Permian: A Case Study

Abstract

Occupational exposure to respirable silica from proppant sand is a risk to field personnel in oil and gas operations. This risk must be mitigated to comply with new OSHA regulations that will take place between 2018 and 2021 for limiting respirable crystalline silica to less than 50 micrograms per liter averaged over across an 8-hr period. Therefore, oil and gas operators, oilfield service companies, and proppant suppliers are poised to employ technologies that can address proppant dust control in the field. Historically, engineering controls have been applied to reduce sand dust using vacuum systems to gather dust in central locations; while other mechanical approaches include limiting sand volumes on conveyer belts or storing sand in silos (necessitating use of a trailer and a storage bin). This paper discusses laboratory and field results from tests designed to mitigate dust that results from handling sand during hydraulic fracturing operations. Coating proppant sand with inert chemical solutions that include a 100% environmentally-friendlybenign chemical blend at transloading rail facilities will be described. Experimental test results to be discussed include lab scale screening of 10+ aqueous and nonaqueous formulations to control dust, sand caking studies, sand flowability, changes in conductivity, bacterial control testing, and chemical compatibility testing with current additive packages used in slickwater and crosslinked gel systems. The outcome of field applications using coated sand samples in the Permian Basin showed up to a 97% decrease of dust generated and levels of employee exposure to respirable crystalline silica less than the revised OSHA PEL of 50 μg/m3 as measured in 10-mm nylon Dorr-Oliver cyclones. A long-term goal for this product is to eliminate the risk of respirable crystalline silica even less than the OSHA action levels at 25 μg/m3 to field staff and to reduce dust exposure to the equipment, improving safety and operational efficiency for operators.